The kinematic hardening is not defined in this model.
material ExpJ2 (1) (2) (3) (4) (5) (6) [7]
# (1) int, unique material tag
# (2) double, elastic modulus
# (3) double, poissons ratio
# (4) double, yield stress
# (5) double, a
# (6) double, b
# [7] double, density, default: 0.0